Power cylinder



June 2, 1964 5. J. MICHALAK, JR 3,135,171

POWER CYLINDER Fileci June 6, 1962 s Sheets-Sheet 1 INVENTOR. STA/V157 d. M/Ll-IALAK 01?.

June 2, 1964 5. J. MICHALAK, JR

POWER CYLINDER Filed June 6, 1962 3 Sheets-Sheet 2 INVENTOR. 57ZIIVZV J. M/C/Mlflk JR.

J1me 1964 s. J. MICHALAK, JR

POWER CYLINDER 3 Sheets-Sheet 5 Filed June 6, 1962 FIG. 9. ,8

' INVENTOR. .emxvzzr J M/c/MMK JR United States Patent 3,135,171 POWER CYLINDER Stanley J. Michalak, In, West Olive, Mich., assignor to Mechanical Power Corporation, Grandville, MiclL, a corporation of Michigan Filed June 6, 1962, Ser. No. 200,396 11 Claims. (Cl. 92--14) This invention relates to fluid cylinders, and especially to a fluid cylinder having a unique pressure amplification and locking means.

'In high speed assembly operations using power cylinders e.g. resistance welding operations, it is desirable to effect a high application pressure, for example to squeeze tightly together parts that are to be welded. Various types of fluid cylinders have been devised heretofore in efforts to achieve-a high power stroke pressure when using relatively low line pressures. One of these is the multiple piston arrangement. This type has only a small pressure amplification, however, in spite of its complexity. A second type is the split nut type in applicants United States Patent 2,625,910, now reissued as United States Reissue Patent Number Re. 25,334. This latter type, while a great improvement over the multiple piston type, still has inherent limitations because of the floating nature of the split nut, the forceful resistance of the coil spring behind the split nut, and other factors inherent in this structure.

It is an object of this invention to provide a fluid cylinder that is capable of effecting :a tremendously high power stroke pressure amplification in multiples of up to 30 or moreover line pressure.

It is another object of this invention to provide a fluid cylinder capable of shifting normally under regular line pressure, and of applying amplified pressure only when triggered by an obstacle encountered by the cylinder shaft. Moreover, the device enables adjustment of the amount of triggering force by the obstacle required to initiate the amplified stroke pressure.

It is another object of this invention to provide a fluid cylinder construction wherein the pressure amplification may be varied widely within the principles of the inven tion to suit the particular use of the structure.

It is another object of this invention to provide a power amplification cylinder having a unique locking means associatedwith a pressure amplification means to prevent slippage during power amplification. The locking means is moreover positively held by an expander means of the pressure amplification means.

It is still another object of this invention to provide a fluid cylinder having a positive, non-slip locking means for the reciprocable shaft to prevent reverse movement under all conditions, except reverse fluid pressure on the piston in the cylinder. The lock-ing means does not jam or cock and applies the locking function over a substantial length to withstand tremendous reverse forces. The locking means does not break loose when the pressure amplification means causes a pressure multiple of many times line pressure on it. Yet, it will quickly and cleanly unlock when reverse fluid line pressure is applied to the piston.

It is another object of this invention to provide a fluid cylinder having a locking action and power amplification, and capable of having long power amplification 3,135,171 Patented June 2, 1964 strokes without the necessity of overcoming increasing severe biasing spring forces when increasing the stroke length. A power amplification of any desired magnitude may therefore be easily and accurately achieved without waste of line fluid pressure to overcome the increasing spring forces. In fact the apparatus provides an adjustable triggering pressure for the power amplification means to suit any particular situation. Once set, the triggering pressure or force required to initiate the pressure amplification remains constant regardless of the power amplification multiple.

It is still another object of this invention to provide a fluid cylinder with a novel type of end cap seal enabling rotation of the end cap to provide any desired orientation of ports in the end caps.

These and other objects of this invention will be apparent upon studying the follow-ing specification in conjunction with the drawings in which:

FIG. 1 is an elevational sectional view of the novel cylinder in the retracted condition;

FIG. 2 is an elevational sectional view of the cylinder with the piston shaft extended, assuming the shaft has struck an abutment and just before the power amplification stroke;

FIG. 3 is an elevational sectional view of the cylinder after the power amplification stroke;

FIG. 4 is a fragmentary, sectional view of a portion of the cylinder showing the reverse movement of the piston assembly;

FIG. 5 is a perspective view of the carrier, locking legs, and helpers of the apparatus;

FIG. 6 is an exploded view of the carrier and a portion of the expander means of the power amplification means:

FIG. 7 is an end view of the carrier from plane V-II- VII of FIG. 6;

FIG. 8 is a perspective view of one of the locking legs;

FIG. 9 is a sectional View of the inner rod and the shaft taken on plane lX-IX of FIG. 3; and

FIG. 10 is a fragmentary, exploded, perspective view of the novel end cap and seal shown on the right end of the cylinder in FIGS. 1, 2 and 3.

Basically, the invention comprises a fluid cylinder having a cylinder housing, a reciprocable piston including an annular sleeve with an inner tapered camrning surface, a reciprocal shaft associated with the piston, an inner locking, serrated rod affixed in the housing over which the shaft, piston and sleeve are adapted to reciprocate, and a unique power amplification and locking means adjacent the piston and cooperating with the shaft and rod. The locking means serves both to hold the shaft in an extended position, and also to lock a portion of an expander means allowing power amplification. The expander means is axially expanded to greatly increase pressure on the shaft in response to a plurality of spreader elements which are radially inwardly shit-table by the tapered sleeve during the power stroke. The locking means provides a positive lock by use of a plurality of pivotal levers or legs which are biased to engagement with the serrated inner rod afiix ed in the cylinder. The levers are normally held against their bias and out of engagement with the rod, by a portion of the sleeve.

When the reciprocal shaft, when extended, encounters an obstacle, the piston becomes disengaged from the stopped rod due to a unique releasable detent means. The piston and camrning sleeve continue to move under fluid pressure to the expander means. One portion of the expander means exerts a greatly increased axial pressure on the shaft, While a second portion shifts slightly to securely lock the ends of the levers into engagement with the serrated rod due to a unique angular interfi-tting between the second portion and levers. Reverse fluid pressure on the piston also reverses the sleeve. Reverse movement of the sleeve depresses the levers against their bias and out of engagement with the serrated rod. This action is aided by unique, biased helpers imparting an axial force on the sleeve to help the sleeve ride over the levers against the bias.

These basic features will be understood more fully by reference to the detailed description to follow.

Referring now to the drawings, FIGS. 1, 2 and 3 show the novel fluid cylinder in its three successive operating stages. FIG. 1 shows the cylinder before fluid'pressure is applied to extend the shaft. FIG. 2 shows the cylinder after fluid pressure is applied to extend the shaft, but before the power stroke causing pressure amplicationoccurs. FIG. 3 shows the cylinder with the shaft extended and the power stroke complete.

The novel cylinder includes a housing 12 having end caps 14 and 16. End cap 14 has a central opening through which the reciprocal shaft 18 extends. End cap 16 includes port 32 communicating with conduit means 34 so that pressurized fluid can communicate with the chamber in the main housing of the cylinders through ports 36 and 38 on the left end of piston assemby 39. End cap 14 includes a port 20 for pressurized fluid to reverse the movement of the piston assembly. This port communicates with conduit 22 which leads into annular conduit 24. Conduit 24 leads'into ports 26 and 28 into the cylindrical chamber on the right end'of the piston assembly as shown.

End cap 16 may be connected to the body 12 of the cylinder by a suitable threaded annular collar 44. An annular seal 46 is utilized. End cap 14 utilizes a different and novel rotatable mounting assembly illustrated more specificallyin FIG. 10. This assembly includes an annular snap ring groovei46 in the inner surface of the cylinder housing 12. A snap ring 48, preferably a True-arc snap ring fits into this groove. Before the snap ring 48 is inserted in this groove, however, an inner fitting 50 is inserted into the cylinder. This fitting includes a central opening 52 through which shaft 18 may extend, and preferably has an O-ring seal 54 around the shaft. Fitting 50 includes a collar portion and a threaded shank 56. Shank 56 interfits into threaded opening 58 of the end cap 14. Annular groove 62 around the end cap enables a sealing compound or element 65 to be placed between it and the cylinder housing 12. This end cap structure has been found particularly advantageous since the end cap assembly 14 may be rotated to any particular desired port orientation. This is extremely helpful when it is desired to align port 20 in a coplanar manner with port 32 on the opposite end of the cylinder to simplify fluid hose attachments. Heretofore, it has been necessary to machine the threads like those on the left end of the cylinder at exact circumferential locations to achieve this alignment. This is no longer necessary. The device can be easily rotated to any position merely-by loosening cap 14- from shank 56, and rotating the assembly, since this loosens the collar of fitting 50 from behind the snap ring. When it is rotated to its desired position, cap '14 is again tightened with respect to fitting 50 to pull the fitting snugly against the snap ring, and seal cap 14 against the end of the cylinder housing 12. If desired, both ends of the cylinder may utilize this type of end cap assembly.

the hex are about the same as the outside diameter of the serrations on the rod 60, so that the serrated portion may freely slide within central opening 66 through hollow shaft 18. This opening 66 in shaft 18 is hexagonal to interfit with hexagonal end 64 of rod 60. This prevents rotation of shaft 18 as it reciprocates over the rod. The cross section of these parts is shown more specifically in FIG. 9.

The cylinder assembly includes, in addition to fixed rod 60 and reciprocal shaft 18, an axial expander means including a first portion 70 fixedly secured to or integral with shaft 18, and second portion 72. This second portion attached to but slightly axially movable on head 76 (FIGS. 5 and 6) of a special carrier element 78. This attachment is made with a snap ring 80 which fits into snap ring groove 82 in head 76 of carrier 78, and inner groove 84 in portion 72. Groove 72 is substantially the same width as the snap ring. However, groove 82 is substantially wider than the snap ring. This allows portion 72 to have slight axial movement on head 76 toward and away from carrier 78. Groove 82 is preferably deep enough to prevent frictional drag as the snap ring moves with portion 72. Movement of portion 72 achieves a unique locking function in a manner to be explained hereinafter. This locking function is also facilitated by frusto-conical or tapered annular surface 88 on portion 72 which cooperates with the like-tapered ends 102 of the pivotal locking legs 90. This angle is preferably approximately 20 with respect to a transverse plane across the cylinder, but may conceivably vary between about 10 to about 45. An angle of 20 has been found to be the most preferred, since it achieves a secure locking action, while still not necessitating a large axial movement of portion 72. This will be understood when the locking actionoperation is described here'inafter.

The locking legs 96 are shown to be two in number, located on the top and bottom of carrier 78. It will be understood that more than two may be utilized, although this number has been found to be very satisfactory for most uses. Each of the locking legs is located within a slot 98 (FIG. 7) and pivotally mounted on 'a shaft at '96. The bottom or radially inner front end 'of each look ing lever or leg includes a serrated surface 100. The adjacent front end surface 102 is at an acute-angle preferably of 20 to cooperate with the acute angle on'surface 88 of expander means portion 72 as explained above. This end 102 extends slightly beyond frusto-conical surface 104 on the carrier, such that when surface 102 and surface'88 are in abutment, surface 104 .is still slightly spaced from surface 88. 0n the opposite end of each leg 90 from the serrated end and on the radially outer edge, is an upper foot 106 which comprises a bearing surface. This surface is adapted'to extend outside' the periphery of cylindrical carrier 78. Beneath'this surface on the radially-inner edge is a cutoutportionlll) into which a biasing element, preferably a resilient pad 112 of a material such as neoprene rubber is placed. This pad tends to bias leg 90 on its pivotto place serrated portion into engagement with serrated rod 60. 'Each of these rubber pads rests upon a thin platform 114 in the carrier and against a back wall 116 (FIG. 6).

In the form of the invention illustrated, the two legs 90 are opposite each other, i.e. 180 apart around the periphery of carrier 78. In the lateral sides of thecarrier 78 is a second pair of slots 120 into which a pair of helper elements 122 are pivotally mountedon shafts 130. Each of these helper elements includes a central camming ridge 124 which is biased to extend above the pehipheral surface of cylinder carrier '79. A biasing spring 128 (FIGS. 5, 6 and '7) under one end of each helper provides the bias. It will of course be understood that a resilient pad may also be used in this instance.

The piston assembly 30 includes a main piston element 14-0 having an annular O-ring seal 142. The piston has an annular collar 144 having a threaded outer surface. To

this threaded surface is attached an annular, elongated sleeve 146 which trails behind piston 140 and is adapted to always reciprocate therewith. Another suitable annular seal 148 may be inserted near the rear end of the sleeve if desired. This sleeve is characterized by an inner, annular tapered, carnming surface 150. It is flanked by a first flat annular surface 152 of a relatively wide diameter adjacent piston 140, and a second fiat annular surface 154 of a smaller diameter at the tail end. It also includes on its tail end, an annular depressor surface 156 of a smaller diameter yet to cooperate with the respective feet 106 of the pivotal legs or locking elements 90. Located between surface 156 and flat surface 154 is an angular bevel 158 which cooperates with ridges 124 (FIG. 5) on the helper elements in a manner to be explained hereinafter.

When the fluid cylinder is in its normal, retracted, inactive, position illustrated in FIG. 1, fiat surface 152 is in contact with a plurality of annularly spaced spreader elements 180 shown as balls. It is conceivable that these may be rollers, toggle elements, or other types of elements than balls provided they can be radially shifted inwardly and outwardly to spread expander portions 70 and 72 apart and allow them to recontract toward each other in a manner to be described hereinafter. These spreader balls 180 are in contact with a pair of facing frustoconical surfaces 71 and 73 on the respective portions 70 and 72.

In a conventional fluid cylinder, the reciprocating piston is integral with or securely fastened to the reciprocal shaft which protrudes out one end cap. However, in this invention, although the piston assembly 30 is normally associated with reciprocal shaft 18, it is separably movable therefrom under certain conditions. Thus, referring to main piston portion 140, this includes an inserted, annular adjustable collar or nut 190 threaded into the body of the piston 140. This collar may include an inner seal 192 around shaft 18. It abuts against spring washer 194. This spring washer in turn holds a plurality of steel balls 196 into annular groove 198 in the outer periphery of shaft 18 near the enlarged, expander portion 70. This groove is seen more specifically in FIG. 6. Because of this arrangement, the piston normally carries shaft along with it, but can move over the shaft independently thereof if the balls 196 are dislodged from groove 198 against the force of spring washer 194. The force required to dislodge these balls radially outwardly is controlled by the amount of pressure applied to the spring washer by adjustable nut 190. Thus, by rotating this nut within piston 140, the biasing force tending to hold the balls in the grooves can be widely varied.

Operation Since the main intended use of this novel fluid cylinder is with resistance welding equipment where two electrodes are pressed together against separate sheet metal portions to be joined, the operation of the apparatus will be described with respect thereto. However, it will be readily realized that the cylinder will have many uses.

When this fluid cylinder is utilized for spot welding, an electrode tip (not shown) is inserted into the open extended end of shaft 18. The electrode tip will cooperate with a stationary electrode tip (not shown) mounted on the opposite side of the sheet metal elements (not shown) to be pressed together and welded. Thus, to weld, shaft 18 must shift to the right as shown. Pressurized fluid connections are made to ports 20 and 32 in end caps 14 and 16. Suitable hoses and nipples of the conventional type may be utilized. A typical fluid line pressure will be approximately 70 pounds per square inch. Suitable valving means (not shown) is utilized to enable pressurized fluid to be first injected into port 32, and then through port 20 to reverse the device. Assuming these arrangements and hook-ups are made, the apparatus is now ready to operate and will appear as it is shown in FIG. 1.

When pressurized fluid is injected into port 32 by opening a suitable valve, the fluid will pass through conduit 34, conduits 36 and 38, and into the main body of the cylinder. It will then exert a pressure on the piston apparatus tending to force it to the right, as illustrated in FIG. 1. The entire piston assembly, including the main piston and its annular sleeve 146 will move. Since balls 196 are in groove 198, shaft 18 will also move. Movement of the shaft carries expander element '70 along. Also, carrier 78 will shift to the right, as well as locking levers 90, helper elements 122, the second expander portion 72, as well as balls 189, all under the air pressure. This shift will occur until the electrode tip in the end of shaft 18 contacts the workpiece which then serves as an abutment. After this shift, the apparatus will appear substantially as shown in FIG. 2. Of course, shaft 60 mounted securely in end cap 16 will remain stationary while the remainder of the apparatus moves thereover. Since end 64 of rod 60 is hexagonal, and opening 66 in shaft 18 is hexagonal, no rotation of the shaft will occur during this reciprocation. This keeps the electrodes properly aligned, even if they are offset from the central axis of the cylinder.

In both the initial position of the cylinder in FIG. 1 and the extended position illustrated in FIG. 2, locking levers 90 are held out of engagement with serrated shaft 60 by inwardly projecting annular surface 156 of sleeve 146 depressing bearing feet 106 against their biasing rubber pads 112.

After the apparatus has shifted to the position illustrated in FIG. 2, although shaft 18 can no longer shift under the influence of ordinary line pressure applied due to the contact of the electrode with the sheet metal workpieces, the line pressure, for example 70 p.s.i., is great enough to cause the piston assembly including sleeve 146 to continue to move. In other words, the pressure applied to the piston and sleeve is greater than the force of the spring washer 194 tending to hold detent balls 196 in groove 198. These balls are thus forced radially outwardly to release the piston assembly from the shaft 18 and allow the former to move over shaft 18 as illustrated in FIG. 3. It will be noted that by adjusting the nut 190, the amount of reverse force which must be applied to shaft 18, i.e. the amount of force differential between shaft 18 and piston assembly 30 which will cause the release of the detent means, can be varied. This is designated herein as the triggering force for the power stroke. For example, it may be desired when welding stiff, slightly bent,

sheet metal parts, to apply a greater pressure to press the parts closely together before triggering the pressure amplification power stroke by release of the piston from the shaft. This is because the pressure multiplication or power stroke is capable of applying extremely high pressure factors only when the elements are in close contact, since the power amplification causes only a very small axial shifting action which would be wasted if the parts were still spaced substantially from each other. This triggering force is therefore accurately governed by adjustment of nut 190 to suit the particular type of workpieces and control the exact conditions under which the initiation or triggering of the power stroke occurs. After the device has shifted to the position in FIG. 2 and the power stroke is triggered by release of ball detent means 196, no further line pressure is required to overcome the movement of the piston and sleeve over shaft 18. In other words, the full line pressure is applied to the piston. Thus, as will be understood, control of the power amplication is determined only by the stroke of sleeve 146, its taper, and the taper of surfaces 71 and 73. As the sleeve moves, the annular inner-flat surface 152 moves past spreader balls 180, and tapered surface beings to pass over spreader balls to force them radically inwardly against facing tapered surfaces 71 and 73. Thus causes spreading of these expander elements 7 0 and 72 and thus a small but very forceful axial movement thereof due to the large mechanical advantage achieved. Simultaneously, since surface 156 of sleeve 146 has moved from engagement with feet 106 of lever locking element 90,

sponge rubber pads 112 thereunder have rotated these locking elements so that their serrated portions 100 interengage with the serrations on shaft 60. However, if any substantial axial stress were to be placed on these levers in this condition, they would tend to slip over the serra tions of rod 60. Therefore, a unique locking feature is provided by portion 72 of the expander means. Since the inner snap ring groove 82 (FIG. 6) of head 76 on carrier '78 is substantially wider than snap ring 80, portion '72 moves slightly to the left as spreader elements 180 apply axial pressure to it. This forces the acute angular surface 38 (FIG. 6) tightly against the front end angular surfaces 102 of locking levers 90 (FIG. 8) to lock the serrations tightly together and prevent any slippage.

As sleeve 146 continues to move over the spreaderelements 180, portion '70 of the expander means moves a limited distance to the right causing a limited movement of shaft 18. This limited movement, however, causes an extreme multiplication of the pressure applied on the electrode tip or whatever else is mounted to the end of shaft 18. It has been found that by utilizing tapers which may vary for example from 10 to 30 on surface 150, and by using reasonable lengths for surface 150, the pressure applied to shaft 18 may be easily multiplied 10, 20, 30 or more times that of the line pressure applied. Thus, for example, with a line presure of 70 p.s.i., applied pressures of over 1,700 p.s.i. may be easily achieved. Moreover, this pressure may be held for any desired period of time Without reverse slippage. More specifically, although the reverse pressure on shaft 18 under these pressure multiplication conditions tends to cause a reverse movement of sleeve 146 as long as the balls are in contact with tapered surface 150, as soon as the balls ride unto flat annular surface 154, this force is all radial and not axial to the cylinder, thereby preventing any tendency to reverse the direction of sleeve 146. When the apparatus is in this extended condition under these high pressures, the locking means holds firmly due to the unique interaction with the expander means, and prevents any reverse slippage of carrier 7 8 and more specifically levers 90 along the fixed serrated rod 60. Thus, no matter how great the pressure is that is applied in a reverse direction on shaft 18, the mechanism will hold in this extended position until it is desired to reverse it.

Moreover, it is a simple matter to reverse the cylinder action. If ordinary line pressure is applied to port 20, reverse pressure is applied to piston assembly 30, causing the piston and sleeve to reverse to the left. Tapered surface 150 allows spreader balls 180 to move radially outwardly again. As soon as flat annular surface 156 of sleeve 146 again reaches the feet 106 of the lever bars 90, it must rotate them out of engagement with serrated rod 60 to allow the entire assembly to move to its initial position. It has been found that under certain conditions, the movement of surface 156 over the top of the bearing surfaces or feet 106 to depress them against their biasing rubber, pads tends to cause the serrated portions to chatter over the rod. This has been alleviated byproviding the unique helper elements 122.

Referring to FIG. 4, the relationship between the several feet and helper surfaces, during reversal is shown. Just as the edge of surface 156 begins to contact protruding feet 106, the ridge 124 of each helper 122 coincides with the beveled edge of sleeve 146. Since the helpers are biased outwardly by their springs 128, the pressure of the ridges causes them to ride up beveled surface 158 to force the sleeve 146 over the carrier in the axial direction of its movement as illustrated by the arrows in FIG. 4. Since the resistance of surface 156 on the feet 106 tends to hold the sleeve back from passing over the carrier, these helpers counteract this effect and cause the feet to be readily depressed without any chatter of the serrated portions over each other. The levers are thus cleanly and quickly unlocked. During unlocking of the levers, portion 72 readily shifts to the right to allow their release, since the balls 180 have moved radially outwardly.

'8 With this unique apparatus, it has been found that extremely high application pressures can be achieved using ordinary line pressures. The power stroke to obtain the desired power pressure amplification is practically unlimited since once the ball detent means is released, the

' piston is free to move over the shaft 18 with no further resistance as far as is needed to control the ultimate pressure. Further, the tapers of the parts can be closely regulated as desired. Moreover, the triggering pressure at which the power amplification initiation occurs can be accurately controlled. Also, the locking apparatus is positive and stable even under extremely high reverse pressure. Finally, there are no floating parts to jam or cock, but rather, smoothly operating parts whose movement is always completely regulated by positive action.

Many other advantages will be apparent to those in the art upon studying the foregoing description and principles. Furthermore, various modifications may occur to those in the art within the principles of the invention taught. These modifications are deemed to be part of this invention, which is to be limited only by the scope of the appended claims and the reasonably equivalent structures to those defined therein.

I claim:

1. A fluid cylinder comprising: a cylinder housing including end closure means; a rod aflixed in said housing; a piston assembly adapted to reciprocate over said rod and including a portion having an inner, axially-tapered camming surface; fluid porting means in said end closure means to enable reciprocation of said piston assembly with fluid pressure; a hollow shaft associated with said piston, extending through one of said end closure means, and adapted to also reciprocate over said rod; locking and pressure amplification means adjacent said piston, including axial expander means operated by radially shifting spreader means; one portion of said expander means being affixed to said shaft; said spreader means adapted to be shifted radially inwardly by said tapered camming surface to axially expand said expander means to amplify pressure on said shaft; pivotally mounted locking levers having portions adapted to engage said rod and adapted to be locked to said rod by said expander means; and carrier means pivotally mounting said locking levers; said piston and sleeve, said shaft, said expander means, and

'said carrier adapted to all be shifted over said rod by fluid pressure, until a reverse axial force is applied to said shaft, and said piston and sleeve adapted to move independently of saidshaft, expander means, and carrier when said reverse axial force is applied, whereby said tapered surface shifts said spreader means radially inwardly to expand said expander means, lock said levers to said rod, and amplify the pressure applied to said shaft.

'2. A fluid cylinder comprising: a cylinder housing including end closure means; a serrated rod affixed in said housing; a piston assembly adapted to reciprocate over said rod and including an annular sleeve having an inner axially tapered camming-surface; fluid porting means in said end closure-means to enable reciprocation of said piston with fluid pressure; a hollow shaft associated with said piston and adapted to also reciprocate over said rod; locking and pressure amplification means adjacent said piston, including axial expander means operated by a plurality of spreader elements; said axial expander means having one portion connected to said shaft, and a second portion expandablymovable with respect to said one portion; a carrier element adjacent said second portion and mounting aplurality of gripping arms adapted to engage and grip said serrated rod; said arms each having an end at anacute angle with respect to a transverse plane across said cylinder; said second portion of said axial expander means having an angular surface interfitting with said arm ends and adapted to securely lock said levers against said serrated rod; and said spreader elements adapted to being shifted radially inwardly by said tapered sleeve when said shaft is extended under fluid pressure and strikes an abutmeat, so that said second portion is axially shifted to hold said arms in locking engagement with said serrated rod, while said first portion is axially shifted in the opposite direction to amplify the pressure of said shaft against the abutment.

3. A fluid cylinder comprising: a cylinder housing including end closure means; fluid port means in said end closure means; a serrated rod affixed centrally in said housing; a piston adapted to reciprocate over said rod and including an axially extending, radially varying camming surface; a hollow shaft extending through one of said end closure means and connected to said piston with a pressure-releasable connecting means; an axial expander means on said shaft having first and second oppositely moving portions; a carriage adjacent said second portion and pivotally mounting a plurality of gripping levers; said second portion adapted to lock said levers in gripping contact with said serrated shaft when moved away from said first portion, and said first portion adapted to shift said shaft a small amount at a high pressure when moved away from said second portion; and radially movable spreader means actuated by said camming surface; said spreading means adapted to be actuated to actuate said expander means when said shaft strikes an abutment causing release of said connecting means, and continued movement of said piston and camming surface.

4. A power cylinder comprising: a cylinder housing including end closure means; fluid port means in said end closure means; a serrated rod aflixed centrally in said housing; a piston adapted to reciprocate over said rod and including an axially extending, radially varying carnming surface; a hollow shaft extending through one of said end closure means and connected to said piston with a pressure-releasable connecting means; said connecting means comprising radially biased detent means adapted to release said piston from said shaft upon the occurrence of a predetermined axial force differential between said piston and shaft so that said piston can then move over said shaft; and locking and pressure amplification means adjacent said piston on said shaft and adapted to be actuated by said camming surface, whereby when said shaft strikes an abutment to cause a differential force between said shaft and piston greater than said predetermined force, said detent means is shifted against its bias to release said piston so that said piston and camming surface continue to move to actuate said locking and pressure amplification means.

5. The power cylinder in claim 4 wherein the biasing force on said detent means is adjustable to allow variations in the force differential necessary to release the piston and camming means.

6. A power cylinder comprising: a cylinder housing including end closure means; fluid port means in said end closure means; a serrated rod aflixed centrally in said housing; a piston adapted to reciprocate over said rod and including an axially extending, radially varying camming surface; a hollow shaft extending through one of said end closure means and connected to said piston with a pressure-releasable connecting means; said connecting means comprising radially oriented, biased detent means adapted to release said piston from said shaft upon the occurrence of a predetermined axial force differential therebetween so that said piston can then move over said shaft; an axial expander means on said shaft having first and second oppositely moving portions; a carriage adjacent said second portion and pivotally mounting a plurality of gripping levers; said second portion adapted to lock said levers in gripping contact with said serrated shaft when expanded, and said first portion adapted to shift said shaft a small amount at a high pressure when expanded; radially movable spreader means actuated by said camming surface; said spreading means adapted to shift said expander means, whereby when said shaft strikes an abutment causing release of said connecting means,

'10 continued movement of said piston and camming surface actuates said expander means to lock said levers to said rod and amplify the pressure on said shaft.

7. A power cylinder comprising: a cylinder housing including end closure means; fluid port means in said end closure means; a serrated rod aflixed centrally in said housing; a piston adapted to reciprocate over said rod and including a sleeve having an axially extending, radially varying camming surface; a hollow shaft extending through one of said end closure means and connected to said piston with a pressure-releasable connecting means; an axial expander means on said shaft having first and second oppositely moving portions; a carriage adjacent said second portion and pivotally mounting a plurality of gripping levers; said levers being biased toward an engaging relationship with said serrated red and having a bearing foot surface engaged by a portion of said sleeve to normally hold said levers out of engagement with said rod; radially movable spreader elements between said first and second portions of said expander means, and adapted to be actuated by the camming surface of said sleeve; said piston and sleeve being releasable from said shaft when said shaft strikes an abutment to create a differential force of predetermined magnitude between said shaft and piston so that said piston and sleeve continues to move; said continued movement causing shifting of said spreader means and actuation of said expander means so that said sleeve releases said biased levers to engage said serrated rod, said first expander portion shifts said shaft a small amount at a high pressure amplification, and said second portion shifts and locks said levers into gripping contact with said rod.

8. The apparatus in claim 7 wherein each of said levers has an end face at an acute angle with respect to a transverse plane through said cylinder, and said second expander portion has a cooperating angular end face which interfits with said lever and faces to lock said levers into engagement with said serrated rod.

9. The apparatus in claim 8 wherein reverse fluid pressure on said piston causes reverse movement of said piston and sleeve so that said sleeve depresses the foot surfaces of said levers against their biasing forces, and wherein said carriage includes a plurality of biased helper elements; said helper elements being adapted to apply axial force on said sleeve tending to force said sleeve over said foot surfaces.

10. A fluid cylinder comprising: a housing including end caps; fluid port means in said end caps; a serrated rod fixed centrally in said housing; a piston adapted to reciprocate over said rod under fluid pressure; an axially-extending, camming element adapted to reciprocate with said piston, and including a radially-varying camming surface; a hollow shaft extending through one of said end caps and connected to said piston with a releasable connecting means releasable under reverse force on said shaft; an axially shiftable expander sleeve adjacent the inner end of said shaft; tapered surface portions between said expander sleeve and shaft end; radially shiftable cam follower rollers positioned adjacent said tapered surface portions to spread said sleeve and shaft when shifted radially inwardly by said camming surface; serrated looking means adjacent to and normally out of engagement with said serrated rod and adapted to lock said sleeve against reverse movement; and said locking means being activated to engage said rod with disconnection of said piston and camming element from said shaft when said shaft strikes an object to cause said follower means when shifted radially inwardly by said camming surface, to force said shaft axially against said object with increased pressure.

11. A fluid cylinder comprising: a housing including end caps; fluid port means in said end caps; a serrated rod fixed centrally in said housing; a piston adapted to reciprocate over said rod under fluid pressure; an axiallyextending, cammingelement'adapted to reciprocate with said piston, and including a radially-varying camming surface; a hollow shaft extending through one of said .end caps and connected to said piston with'a releasable connecting means; an axially shiftable-sleeve adjacent the inner end of said shaft; tapered surface portions between said sleeve and-shaft end; radially'shiftable cam follower means positioned adjacent said tapered surface portions .to-spread said sleeve and shaft when shifted radially inwardl-y by said'carnrning surface; locking means positioned radially adjacent said serrated rodand normally out of ated to shift radially inwardly when said shaft'is stopped by an external object causing disconnection of said piston,

*and'continuedmovement ofsaidpiston and said camming element under fluid pressure, to look behind said shaft and preventreverse movement thereof until reverse fluid pressure is applied.

No references cited. 

1. A FLUID CYLINDER COMPRISING: A CYLINDER HOUSING INCLUDING END CLOSURE MEANS; A ROD AFFIXED IN SAID HOUSING; A PISTON ASSEMBLY ADAPTED TO RECIPROCATE OVER SAID ROD AND INCLUDING A PORTION HAVING AN INNER, AXIALLY-TAPERED CAMMING SURFACE; FLUID PORTING MEANS IN SAID END CLOSURE MEANS TO ENABLE RECIPROCATION OF SAID PISTON ASSEMBLY WITH FLUID PRESSURE; A HOLLOW SHAFT ASSOCIATED WITH SAID PISTON, EXTENDING THROUGH ONE OF SAID END CLOSURE MEANS, AND ADAPTED TO ALSO RECIPROCATE OVER SAID ROD; LOCKING AND PRESSURE AMPLIFICATION MEANS ADJACENT SAID PISTON, INCLUDING AXIAL EXPANDER MEANS OPERATED BY RADIALLY SHIFTING SPREADER MEANS; ONE PORTION OF SAID EXPANDER MEANS BEING AFFIXED TO SAID SHAFT; SAID SPREADER MEANS ADAPTED TO BE SHIFTED RADIALLY INWARDLY BY SAID TAPERED CAMMING SURFACE TO AXIALLY EXPAND SAID EXPANDER MEANS TO AMPLIFY PRESSURE ON SAID SHAFT; PIVOTALLY MOUNTED LOCKING LEVERS HAVING PORTIONS ADAPTED TO ENGAGE SAID ROD AND ADAPTED TO BE LOCKED TO SAID ROD BY SAID EXPANDER MEANS; AND CARRIER MEANS PIVOTALLY MOUNTING SAID LOCKING LEVERS; SAID PISTON AND SLEEVE, SAID SHAFT, SAID EXPANDER MEANS, AND SAID CARRIER ADAPTED TO ALL BE SHIFTED OVER SAID ROD BY FLUID PRESSURE, UNTIL A REVERSE AXIAL FORCE IS APPLIED TO SAID SHAFT, AND SAID PISTON AND SLEEVE ADAPTED TO MOVE INDEPENDENTLY OF SAID SHAFT, EXPANDER MEANS, AND CARRIER WHEN SAID REVERSE AXIAL FORCE IS APPLIED, WHEREBY SAID TAPERED SURFACE SHIFTS SAID SPREADER MEANS RADIALLY INWARDLY TO EXPAND SAID EXPANDER MEANS, LOCK SAID LEVERS TO SAID ROD, AND AMPLIFY THE PRESSURE APPLIED TO SAID SHAFT. 